Method of making a radio frequency identification tag

ABSTRACT

The invention is a radiofrequency identification tag comprising a semiconductor chip having radio frequency, logic, and memory circuits, and an antenna that are mounted on a substrate. The antenna may be used by the chip to modulate an incident RF signal to transfer information to a base station. The antenna comprises one or more lengths of thin wire that are connected directly to the chip by means of wire bonding. The chip and antenna combination are sealed with an organic film covering.

This is a divisional application of application Ser. No. 08/303,976,filed Sep. 9, 1994, now U.S. Pat. No. 5,682,143.

FIELD OF THE INVENTION

This invention relates to the field of radio frequency (RF) tagging.More specifically, the invention relates to the making of an improvedsmall size, low cost RF tag that transmits multiple bits of information.

BACKGROUND OF THE INVENTION

In general, circuitry is manufactured on hard printed circuit boards orflexible substrates. Printed circuit boards include materials likeepoxy-resin or epoxy-glass boards. One generic class on which thesecircuits are manufactured is FR4. Alternatively flexible substrates,also called "flex", include structures of copper on polyimide. Thesecircuits are generally used in automobiles, consumer electronics, andgeneral interconnections.

A well known technology for attaching semiconductor circuits, or "chips"to the circuit board or flex structures is called wirebonding. Wirebonds are made from small diameter wires in the range of 25 microns indiameter and are very short. Generally the wire bonds are on the orderof 1 millimeter (mm) in length. These wire bonds are normally kept shortfor several reasons:

1. The small diameter of the wire makes it very weak.

2. In typical circuits many bonds are made and longer lengths would makethe connections more prone to electrical shorting.

3. Longer lengths of the wires increase self and mutual inductance whichdegrade the electrical performance of the circuit.

Radio Frequency Identification (RF ID) is just one of manyidentification technologies for identifying objects. The heart of the RFID system lies in an information carrying tag. The tag functions inresponse to a coded RF signal received from a base station. The tagreflects the incident RF carrier back to the base station. Informationis transferred as the reflected signal is modulated by the tag accordingto its programmed information protocol.

The tag consists of a semiconductor chip having RF circuits, logic, andmemory. The tag also has an antenna, often a collection of discretecomponents, capacitors and diodes, for example, a battery in the case ofactive tags, a substrate for mounting the components, interconnectionsbetween components, and a means of physical enclosure. One variety oftag, passive tags, has no battery. They derive their energy from the RFsignal used to interrogate the tag. In general, RF ID tags aremanufactured by mounting the individual elements to a circuit card. Thisis done by using either short wire bond connections or solderedconnections between the board and the circuit elements: chip,capacitors, diodes, antenna. The circuit card may be of epoxy-fiberglasscomposition or ceramic. The antennas are generally loops of wiresoldered to the circuit card or consist of metal etched or plated on acircuit card. The whole assembly may be enclosed in a plastic box ormolded into a three dimensional plastic package.

While the application of RF ID technology is not as widespread as otherID technologies, barcode for example, RF ID is on its way to becoming apervasive technology in some areas, notably vehicle identification.

Growth in RF ID has been inhibited by the absence of infrastructure formanufacturing the tags, the high cost of tags, the bulkiness of most ofthe tags, problems of tag sensitivity and range, and the need for thesimultaneous reading of multiple numbers of tags. A typical tag costs inthe $5 to $10 range. Companies have focused on niche applications. Someprior art is used to identify railway boxcars. RF tags are now used inthe automatic toll industry, e.g. on thruway and bridge tolls. RF tagsare being tested for uses as contactless fare cards for buses. Employeeidentification badges and security badges have been produced. Animalidentification tags are also commercially available as are RF ID systemsfor tracking components in manufacturing processes.

One limitation of making RF tags made from PC boards or flex is that theflex or boards must be manufactured first. For very high volumes of tags(greater than one hundred million tags) new factories must be built toaccommodate the capacity needed for board or flex production to meet tagdemand. Further, RF tags made from these technologies are too expensivefor many applications. For example, bar codes are a technology that isused for identification at a much lower cost than existing RF taggingtechnology.

OBJECTS OF THE INVENTION

An object of this invention is the making of an improved radio frequencyidentification tag.

An object of this invention is the making of an improved, low cost radiofrequency identification tag that is made from commodity materials.

Another object of this invention is the making of an improved radiofrequency identification tag that can be manufactured in very largequantities.

SUMMARY OF THE INVENTION

The present invention is a method of making a novel radio frequency (RF)tag that comprises a semiconductor circuit that has logic, memory, andradio frequency circuits. The semiconductor is mounted on a substrateand is capable of receiving an RF signal through an antenna that iselectrically connected to the semiconductor through connections on thesemiconductor.

The antenna is novel, has a novel structure, and is constructed by anovel use of wire bonding techniques. The antenna is one or more wires,each connected to the semiconductor connections by one or two wirebonds. (In a preferred embodiment, the antenna is made of a pair orplurality of pairs of wires.) The wire bonding method and resultingstructure, rather than having another connection made at the end of ashort wire, spools out a length of wire required by the antenna design,and cuts the second end of the wire without making any electricalconnection at the second cut end. In some preferred embodiments, thesecond cut end of the wire is held in place by attaching the cut end tothe substrate with adhesive or by local heating of the substrate. Inthis way, the wire bonding method is used to actually create a componentof the RF tag circuit (the antenna) and not merely to connect twocomponents. The resulting novel antenna structure is a long wireconnected to the circuit by a wire bond. The components of the novel RFtag are then covered in an organic cover that has a novel use in thistype of device.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an isometric drawing of the present invention showing oneembodiment of a radio frequency tag with a single antenna.

FIG. 2 is an isometric drawing of the present invention showing oneembodiment of a radio frequency tag with multiple antennas.

FIG. 3 is an isometric drawing of the present invention showing oneembodiment of a radio frequency tag with multiple antennas oriented in adifferent direction with respect to each other.

FIG. 4 is an isometric drawing of one embodiment of the presentinvention showing a radio frequency tag with a single loop antenna.

FIG. 5 is an isometric drawing of one embodiment of the presentinvention showing a radio frequency tag with multiple loop antennas.

FIG. 6 is an isometric drawing of the present invention showing a radiofrequency tag with a single loop antenna, where cutout tabs secure theends of the antenna.

FIG. 7 is a top view drawing of the present invention showing a radiofrequency tag with a single loop antenna, where cut out tabs securelocations on the antenna so that the antenna has an orientation in twodimensions.

FIG. 8 is a top view drawing of the present invention showing oneembodiment of a radio frequency tag with multiple antennas.

FIG. 9 is a top view drawing of the present invention showing oneembodiment of the present invention showing two tags with loop antennason one substrate.

FIG. 10 is an isometric drawing of the present invention showing a radiofrequency tag with a single loop antenna, where studs secure the ends ofthe antenna.

FIG. 11 is a flow chart showing the method steps of the presentinvention;

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 is a drawing of a novel radio frequency tag 100 that is made inaccordance with the method of this invention and comprises a substrate141, a semiconductor circuit or chip 111, a first connection or contact121, a second connection or contact 122, a first wire 131 bound to thefirst connection 121 by a bond 131A, and a second wire 132 bound to thesecond connection 122 by a bond 132A. These components are covered by anorganic cover 151 that serves as environmental protection for theantenna 133 comprising wires (131, 132) and bonds (131A, 132A), andcircuit 111.

The substrate 141 is made from an organic film. A preferred film ispolyester also known as mylar (Mylar is a trademark of Dupont). Anotherpreferred film is polyimide also known as Kapton (Kapton is a trademarkof Dupont). Such materials are used as substrates 141 and are well knownin the art.

The semiconductor circuit 111 has a memory, logic circuits, and radiofrequency (RF) circuits and in a preferred embodiment has no battery.Circuits like this used for RF tags are well known and commerciallyavailable. In step 1110 of FIG. 11, the semiconductor circuit or chipcan be attached to the substrate by means of adhesive or reflowing thesubstrate 141 by local heating. The semiconductor also has one or moreof connections or contact (121 and 122). The contacts (121 and 122)provide an input and output (I/O) connection to the RF circuitry of thesemiconductor. The connections 121 and 122 have an impedance that can bevaried by logic in the semiconductor 111. When an RF signal sent to theRF tag is sensed by a circuit in the semiconductor 111, a logic circuitin the semiconductor 111 causes the impedance between the contacts tochange according to some pre-programmed logic. This impedance changemodulates the RF signal reflected from the RF tag. This modulationallows the RF tag to send information back to a base station whichoriginally sent the RF signal. An antenna connected to the semiconductor111 plays an essential part in the reception of the RF signal andtransmission (reflecting back) of the modulated RF signal. The presentinvention is a novel antenna and semiconductor structure.

One preferred antenna and semiconductor structure is shown as wires 131and 132 connected to connections 121 and 122 respectively. In thisembodiment the wires are connected by wire bonding (FIG. 11, step 1120)at bond locations 131A and 132A, respectively. While connecting wireswith wire bonding is well known, wire bonding techniques heretofore havenot been used to create component structures of a circuit as in thepresent invention. In this invention, the wire bonding creates a novelantenna (FIG. 11, step 1130) and connection structure that matches thetransmission (signal reflection) and reception requirements of thesemiconductor circuit 111.

In this embodiment, each wire is connected by wire bonding techniques(FIG. 11, step 1120 at one bond connection (131A and 132A,respectively), unspooled to a specified length (FIG. 11, step 1130), andthen cut, where the cut end of each wire is left unconnected. The cutcan be performed by any well known method used by wire bonding machines,including knife blade (swedge, guillotine), mechanical chopper,mechanical pincers, laser, etc. Furthermore, the wires 131 and 132 canbe connected at the bond points (131A and 132A) by means other than wirebonding including: laser, soldering, and conducting epoxy.

The cut end of the wire can be held in place (FIG. 11 step 1140) inseveral ways. The cut end of the wire can be held in place on thesubstrate by a small spot of adhesive 169 placed below the cut end. Thecut end could also be held in place by locally heating the substrate atthe point where the cut end rests so that the substrate becomes stickyand adheres to the cut end. Localized heating of substrates is wellknown and includes spot application of heat with tools or a laser beamfocused at the point of heating. Adhesives are also well known. Theyinclude epoxies, silicones, and phenolic-butaryl.

A further way of attaching the cut end to the substrate (FIG. 11, step1140) involves heating the wire (131, 132) so that the cut end heats upthe substrate at the point of contact and causes the cut end to attachto the substrate. The wire can be heated by inductive heating, resistiveheating, laser heating, or any other method used for this purpose.Alternatively, a portion of the substrate under the wire can be heatedso that part or all of the wire becomes embedded in the substrate. Thiseffect can also be accomplished by heating the wire and applyingpressure to part (or all) of the wire so that part (or all of the wire(131, 132) becomes embedded in the substrate.

Using this novel structure, RF tag antenna components can bemanufactured by only using commodity materials, i.e., wire used for wirebonds by wire bonding machines and unpatterned organic plastic (likepolyester) for the substrate. No circuit boards or patterned flexiblesubstrate material is required. Since only commodity materials (wire andorganic plastic) are needed to produce these novel tag structures, largequantities (greater than 100 million) of tags can be manufacturedinexpensively without being limited by the existing manufacturinginfrastructure.

The length of the wire (131, 132) is determined by the frequency of theRF signal at which the RF tag is to be operated. These frequencies canbe any frequency that can be transmitted. However, in a more preferredembodiment, the frequencies lie in a range above 300 Megahertz. In thisrange of frequencies antenna of reasonable length can be constructed tobe resonant. A even more preferred range of frequencies is between 900Megahertz to 20 Gigahertz. The most preferred frequencies are thosepermitted for RF tag use by the Federal Communications Commission, someof which include 0.915, 1.92, 2.45, and 5.0 Gigahertz.

To produce a preferred resonant antenna, the lengths (162, 163) of thetwo wires (131, 132) comprising the antenna are equal. In a preferredembodiment, each of the lengths, (162, 163) is one quarter wavelengthlong. More specifically, the length of each wire is equal to (c/4)×f,where c is the speed of light and f is the radio frequency 105 that theRF tag is operating at. In practice, the length will be slightly less(by a factor of approximately 5%) to account for capacitance effects.Similarly, the sum of the lengths of 162 plus 163 is one halfwavelength, where the total length to be used in practice is0.95×(c/2)×f. Hereafter, when a specific length is referred to, it willbe the total of the wavelengths (162 plus 163) or a half-wavelengthlength. A preferred range of total antenna wire (131,132) lengths (162,163) is between 10 millimeters and 1000 millimeters in length. A morepreferred range of antenna wire lengths is between 28 mm and 150millimeters. Specific preferred lengths (162, 163) of the antenna wires(131, 132) are 150 mm, 74 mm, 58 mm, 28 mm lengths that match therespective frequencies above.

The wire used to construct the antennas is that which is commonly usedfor short wire bond connections. The wire diameter 170 may be between 25microns inch and 250 microns (FIG. 11 step 1120). The wire may becomposed of aluminum alloy, copper alloy, gold alloy, copper,gold-plated copper or gold. Such wire is commercially available frommany sources, e.g., the American Fine Wire Company of Selma, Alabama.Aluminum-alloy wire is preferred because of its low cost. Alternatematerials may be chosen based cost, availability, and bondability to thechip contact pads. Use of this type of wire with this diameter in themanufacture of RF tag antennas is thought to be novel.

Adhesive 161 in FIG. 1 secures substrate 141 to cover layer 151 (FIG.11, step 1150). The adhesive serves to hold the chip and wires in placeand to seal the package. By using adhesive over the entire substrate,not just the edges of the package, voids which may accumulate moistureare not allowed to form. Since moisture will accelerate corrosion, theexclusion of moisture will improve the reliability of the package.Adhesives commonly used in the semiconductor industry include epoxies,silicones, and phenolic-butyral. A unique aspect of this package is touse a low-melting point polymer as a preferred adhesive, EVA or ethylvinyl acetate. EVA is well known in the bookbinding and food industriesbut its use in the semiconductor industry in RF tag structures isthought to be novel. In various preferred embodiments, the adhesive 161can be placed locally on the substrate around the components (antenna,semiconductor), or placed on the cover 151 before the cover is placed onthe substrate 141.

The antenna (131, 132), the semiconductor 111, and the substrate 141 areencapsulated by a organic cover 151 (FIG. 11, step 1150) using a noveltechnique for the RF tag art. These components are placed in alaminating machine that applies an organic material (ethyl vinylacetate) heated enough to become soft and sticky as it is applied withpressure to the structure. In this way, voids in the non-planar surfaceare filled with the organic material. In a more preferred embodiment,the organic material comprises two layers, one of organic material 151and another of organic adhesive 161. In this case the heat and pressureare also applied. The heat causes the adhesive to flow to fill the voidson the non-planar surface of the structure. An alternative preferredembodiment uses a pressure sensitive adhesive without the heating.

FIG. 2 is a drawing of a novel radio frequency tag 200 that comprises asubstrate 141, a semiconductor circuit 211, a first connection 221, asecond connection 222, third connection 223, a fourth connection 224, afirst wire 231 bound to the first connection 221 by a bond 231A (FIG.11, step 1120), and a second wire 232 bound to the second connection 222by a bond 232A (step 1120), and a third wire 233 bound to the thirdconnection 223 by a bond 233A (step 1120), and a fourth wire 234 boundto the fourth connection 224 by a bond 234A (step 1120). Thesecomponents are covered by an organic cover 151 that serves asenvironmental protection for the wires (231-234) and bonds (231A-234A)and circuit 211 (step 1150). These bonds (231A-234A) are wire bonds(step 1120) as described above or their equivalents.

This diagram incorporates more than two wires (231-234) to form multiplesets of antennas (231-232 and 233-234), e.g., antenna 241 compriseswires 231 and 232 and antenna 242 comprises wires 233 and 234. Themultiple antennas increase the strength of the signal received by thechip 211 and provide a measure of redundancy. The antennas may be ofdifferent lengths in order to be resonant at different frequencies.

FIG. 3 is a drawing of a novel radio frequency tag 300 that comprises asubstrate 141, a semiconductor circuit 311, a first connection 321, asecond connection 322, third connection 323, a fourth connection 324, afirst wire 331 bound 321A to the first connection 221 (step 1120), and asecond wire 332 bound 322A to the second connection 322 (step 1120), anda third wire 333 bound 323A to the third connection 323 (step 1120), anda fourth wire 334 bound 324A to the fourth connection 324 (step 1120).These components are covered by an organic cover 151 that serves asenvironmental protection for the wires (331-334) and bonds (321A-324A)and circuit 311 (step 1150). In the preferred embodiment, the bonds arewire bonds (321A-324A) (step 1120) or their equivalents as describedabove.

In FIG. 3, the pairs of wires (331, 333 and 332, 334) are arranged in adifferent, non parallel direction from each other, preferablyperpendicular so as to maximize the reception and transmission of radiofrequency energy in directions perpendicular to each other. Thiseliminates nulls in the reception/transmission pattern.

FIG. 4 is a drawing of a novel radio frequency tag 400 that comprises asubstrate 141, a semiconductor circuit 411, a first connection 421, asecond connection 422, a wire 431 bound to the first connection 421 by abond 421 A at one end of the wire, and the same wire 431 bound to thesecond connection 422 by a bond 422A at the other end of the wire 431.These components are covered by an organic cover 151 that serves asenvironmental protection for the wire 431, bonds (421A, 422A), andcircuit 411. In the preferred embodiment, the bonds (421A, 422A) arewire bonds or their equivalent as described above. In another preferredembodiment, a polymeric encapsulant 405 provides a encapsulation for thechip, is used to insulate adjacent conductors from each other, improvesvibration and shock resistance, provides mechanical rigidity to thedevice and connections, and provides protection from atmospheric attackand dust. Preferably this polymeric encapsulant is opaque to protectlight sensitive circuit and forms a thin layer of protection 100 microns(4 mils).

In this diagram, the wire 431 is arranged to form a single loop antenna433. This antenna will have a higher impedance than that of the antenna133 (comprising wires 131 and 132 as shown in FIG. 1). It may thustransfer more energy to a high-impedance input circuit on chip 411. Theloop is created by moving the wire 431 with the wire bonding tool. In apreferred embodiment, the wire is held in place on the substrate by anadhesive on the substrate to help in the formation of the loop.

FIG. 5 is a drawing of a novel radio frequency tag 500 that comprises asubstrate 141, a semiconductor circuit 511, a first connection 521, asecond connection 522, a wire 531 bound to the first connection 521 by abond 531A at one end of the wire, and the same wire 531 bound to thesecond connection 522 by a bond 532A at the other end of the wire. Asecond loop antenna is formed with a third connection 523, a fourthconnection 524, a wire 536 bound to the third connection 523 by a bond533A at one end of the wire 536, and the same wire 536 bound to thefourth connection 524 by a bond 534A at the other end of the wire 536.These components are covered by an organic cover 151 that serves asenvironmental protection for the wires (531, 536) the bonds (531A-534A),and circuit 511. The bonds are wire bonds as described above or theirequivalents.

The addition of a second loop antenna increases the sensitivity of thetag by increasing the total strength of the signal received.

FIG. 6 is a drawing of a novel radio frequency tag 600 that comprises asubstrate 141, a semiconductor circuit 611, a first connection 621, asecond connection 622, a wire 631 bound 631A to the first connection 621at one end of the wire 631 and the same wire 631 bound 632A to thesecond connection 622 at the other end of the wire. These components arecovered by an organic cover 151 that serves as environmental protectionfor the wire 631, the bonds (631A and 632A), and circuit 611. Thesubstrate 141 is provided with punched notches 681 and 682 which providemeans for retaining the wire at its ends to hold the wire in placeduring manufacture. A punched notch 681 is cut in the substrate so thatit produces a bendable flap 685 which can hold the wire as it is looped.This cut can be produced by a punch tool. An air jet 687 would displacethe flap, i.e., bend it from the substrate until the wire could belooped between the bent flap 685 and the remaining substrate.

FIG. 7 is a top view drawing of a novel radio frequency tag 700 thatcomprises a substrate 141, a semiconductor circuit 711, a firstconnection 721, a second connection 722, a wire 731 bound to the firstconnection 721 and the same wire 731 bound to the second connection 722.These components are covered by an organic cover 151 that serves asenvironmental protection for the wire 731, the bonds, and circuit 711.The substrate 141 is provided with punched flaps 781, 782, 783, and 784which allow wire 731 to be held in place during manufacture.

Note that the preferred embodiment of the radio frequency tags in thisdisclosure are passive, i.e., there is no battery on the substrate 141.However, an alternative embodiment is an active tag, as shown in FIG. 7,where a battery 791 is connected to the semiconductor 711 at connections723, 724 in order to provide on board power to the semiconductor 711.

FIG. 8 is a top view drawing of a novel radio frequency tag 800 thatcomprises substrate 141, a semiconductor chip 811, with contacts 810,and 815. Wires 821, 823, and 824 are bonded to contact 810. Wires 825,826, and 827 are bonded to contact 815. These components are covered byan organic cover 151 that serves as environmental protection for thewires 821, 823, 824, 825, 826, and 827, the bonds and circuit 811.

FIG. 9 is a top view drawing of a novel radio frequency tag 900 thatcomprises substrate 141, two semiconductor chips 910 (and 911), withcontacts 915 and 916 (917 and 918). Wires 970 (and 980), are bonded tocontacts 915 and 916 (917 and 918). Wire 970 is connected from contact915 around punched flaps 930 and 940 to contact 916 in substrate 141.Wire 980 is connected from contact 917 around punched flaps 960 and 950to contact 918 in substrate 141. These components are covered by anorganic cover 951 that serves as environmental protection for wires 970and 980, the bonds, and circuits 910 and 911.

FIG. 10 is a drawing of a novel radio frequency tag 1000 that comprisessubstrate 141, semiconductor chip 1011 with contacts 1021 and 1022. Wire1031 is bonded to contact 1021 by bond 1021A and wrapped around embossedpillar 1091 and 1092 and then bonded to contact 1022 by bond 1022A.These components are covered by an organic cover 1051 that serves asenvironmental protection for wire 1031, the bonds and circuit 1011. Thesubstrate is provided with raised studs or dimples which provide meansfor retaining the wire at its ends to hold the wire in place duringmanufacture while the wire 1031 is looped. The studs can be made using aheated die or punch to make part of the substrate deform to the diecontour so that the stud or dimple (1091, 1092) protrudes above thesurface of the substrate. This technique and equivalents are common inthe art, e.g. the embossing techniques used to create raised letters ona plastic credit card. The studs may also be created by adding apreformed piece to the substrate. One preferred added piece would be amolded plastic.

In a more preferred embodiment, pillars 1091 and 1092 are made with atool that deforms the substrate 141 at an acute angle with the substrateso that the angle opens away from the chip 1011. In this way the wire1031 will not slip off of the pillars 1091 and 1092 before the cover1051 is applied. In an alternative preferred embodiment, the pillars1091 and 1092 are made so that the tops are larger in diameter than thebottoms (the portion closest to the top surface of the substrate.) Thiscan be done by applying pressure on the tops of the pillars to flare thetop.

It is evident that one skilled in the art given this disclosure coulddevelop equivalent embodiments which are also within the contemplationof the inventors.

We claim:
 1. An improved method of making a radio frequency tag whichincludes a semiconductor device with at least one pair of contacts andan antenna electrically connected to at least one pair of said at leastone pair of contacts, the semiconductor device modulating andretransmitting a radio frequency signal received by the antenna, theimproved method comprising the steps of:attaching said semiconductordevice to a supporting substrate; forming said antenna entirely of atleast one wire having a diameter in the range of 25 microns to 250microns by spooling wire from and positioning the spooled wire with awire bonding machine; wire bonding said antenna to at least one pair ofsaid at least one pair of contacts of said semiconductor device usingsaid wire bonding machine; and attaching said antenna for support tosaid supporting substrate.
 2. The improved method of claim 1 whereinsaid semiconductor device is attached to said supporting substrate by achip-attaching adhesive.
 3. The improved method of claim 1 wherein saidantenna is attached to said supporting substrate by a wire-attachingadhesive.
 4. The improved method of claim 1 and further comprising thestep of encapsulating said semiconductor device and said contact.
 5. Theimproved method of claim 1 and further comprising the step of attachinga top cover to said supporting substrate to entirely enclose saidsemiconductor device and said antenna between said supporting substrateand said top cover.
 6. The improved method of claim 5 wherein said topcover is formed of an organic material.
 7. The improved method of claim5 wherein said top cover includes an outer layer and an inner layer,said outer layer being an organic film and said inner layer being acover adhesive.
 8. The improved method of claim 5 wherein said top coveris attached to said supporting substrate using heat.
 9. The improvedmethod of claim 8 wherein said top cover is attached to said supportingsubstrate using pressure in addition to said heat.
 10. The improvedmethod of claim 1 wherein said antenna is formed of a single length ofwire spooled from said wire bonding machine.
 11. The improved method ofclaim 1 wherein more than one said radio frequency tag is formed on asingle supporting substrate.
 12. An improved method of making a radiofrequency tag which includes a semiconductor device having at least twocontacts and an antenna electrically connected at least to two contactsof said at least two contacts, the semiconductor device modulating andretransmitting a radio frequency signal received by the antenna, theimproved method comprising the steps of:attaching said semiconductordevice to a supporting substrate; forming said antenna entirely of wirehaving a diameter in the range of 25 microns to 250 microns by spoolingwire from and positioning the spooled wire with a wire bonding machine;wire bonding ends of said antenna to said two contacts of said at leasttwo contacts of said semiconductor device using said wire bondingmachine; and attaching said antenna for support to said supportingsubstrate.
 13. An improved method of making a radio frequency tag whichincludes a semiconductor device having two contacts and an antennaelectrically connected to said two contacts, the semiconductor devicemodulating and retransmitting a radio frequency signal received by theantenna, the improved method comprising the steps of:attaching saidsemiconductor device to a supporting substrate; forming said antennaentirely of wire having a diameter in the range of 25 microns to 250microns by spooling wire from and positioning the spooled wire with awire bonding machine; wire bonding ends of said antenna to said twocontacts of said semiconductor device using said wire bonding machine;and attaching said antenna for support to said supporting substrate. 14.The improved method of claim 13 wherein said semiconductor device isattached to said supporting substrate by a chip-attaching adhesive. 15.The improved method of claim 13 wherein said antenna is attached to saidsupporting substrate by a wire-attaching adhesive.
 16. The improvedmethod of claim 13 and further comprising the step of encapsulating saidsemiconductor device and said two contacts.
 17. The improved method ofclaim 13 and further comprising the step of attaching a top cover tosaid supporting substrate to entirely enclose said semiconductor deviceand said antenna between said supporting substrate and said top cover.18. The improved method of claim 17 wherein said top cover is formed ofan organic material.
 19. The improved method of claim 17 wherein saidtop cover includes an outer layer and an inner layer, said outer layerbeing an organic film and said inner layer being a cover adhesive. 20.The improved method of claim 17 wherein said top cover is attached tosaid supporting substrate using heat.
 21. The improved method of claim20 wherein said top cover is attached to said supporting substrate usingpressure in addition to said heat.
 22. The improved method of claim 13wherein said antenna is formed of a single length of wire spooled fromsaid wire bonding machine.
 23. The improved method of claim 13 whereinsaid antenna is formed of a plurality of lengths of wire all spooledfrom said wire bonding machine.
 24. The improved method of claim 13wherein said antenna includes a length of wire spooled from said wirebonding machine, said length of wire having two ends and said two endsof said wire being wire bonded respectively to different ones of saidtwo contacts of said semiconductor device using said wire bondingmachine.